The invention relates to a screwed assembly, consisting of at least one pre-punched upper component and one unpunched lower component, an intermediate layer arranged therebetween, and also multiple fastening screws which are each inserted via a pre-punch into the upper component and, with the intermediate layer interposed, are screwed together with the unpunched component.
Such a screwed assembly for motor vehicle body parts is known from EP 2 311 713 A1, in which an outer, pre-punched steel flange is connected to an internal aluminum tube in a load-resistant manner via self-tapping fastening screws and an adhesive layer. The self-tapping fastening screws are inserted from the side of the pre-punches into the steel flange. In this case, the fastening screws are frequently tightened in the still uncured state of the adhesive layer for manufacturing reasons, with the result that the adhesive material can be displaced in an uncontrolled manner.
The object of the invention is to implement a screwed assembly of the claimed type so that interfering material movements of the intermediate layer, i.e., in particular the adhesive layer, which is uncured during the tightening of the screw connections, can be suppressed in a structurally simple manner.
This and other objects are achieved according to the invention by the screwed assembly consisting of at least one pre-punched, upper component and one unpunched, lower component, an intermediate layer arranged therebetween, and multiple self-tapping fastening screws, which are each inserted via a pre-punch into the upper component and are screwed together in the uncured state of the intermediate layer with the unpunched component, wherein the pre-punches in the upper component are implemented as blind holes closed by a web.
According to the invention, the pre-punch through the thin-walled pre-punch web in conjunction with the fastening screw which penetrates through the pre-punch web is securely closed in a simply manufactured manner. Thus, the intermediate layer material is effectively prevented from exiting from the pre-punch and material particles are prevented from being able to be spun away outward onto the component surface or into the surroundings by the rotating fastening screw. But, nonetheless, it is ensured that the tightening torque and the drilling length of the self-tapping fastening screw, independently of the wall thickness of the upper component on the screw head side, remain unchanged within the limits predefined by the screw connection to the unpunched, lower component.
In a further advantageous embodiment of the invention, the pre-punch web is arranged at a point of the pre-punch which is remote from the component surface on the intermediate layer side. Thus, a compensation chamber delimited on the outside by the pre-punch web results, into which excess intermediate layer material, specifically in particular adhesive material, can escape without force during the tightening of the fastening screw.
With regard to a further manufacturing simplification, the pre-punched component is expediently a cast part, preferably made of aluminum, so that the pre-punch web can also be molded on to the component during the casting operation without subsequent machining.
For reasons of a high-strength and, at the same time, chip-free screw connection, it is finally advisable to use flow drilling screws as the self-tapping fastening screws.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.